1. Field of the Invention
The present invention relates to an adhesive sheet for producing a semiconductor device.
2. Description of the Related Art
In recent years, stacked multi chip packages have been spread, wherein memory package chips for portable telephones or portable audio instruments are stacked into a multi-level. With progress in image processing technique or multi-functionalization of portable telephones and other instruments, an increase in the density and the integration degree of packages therefor has been promoted, as well as a decrease in the thickness thereof.
Meanwhile, when a cation (for example, a copper ion or iron ion) is mixed from the outside into a crystal substrate of a wafer in any process for semiconductor-production and then the cation reaches a circuit-forming area formed in the upper surface of the wafer, there is caused a problem that the electrical characteristic thereof is declined. When a semiconductor product is used, there is also caused a problem that a cation is generated from its circuit or wires so that the electrical characteristic is deteriorated.
Against the problems, the following attempts have been hitherto made: extrinsic gettering of working the rear surface of a wafer to form a fractured layer (strain), and capturing cations by the fractured layer so as to remove the cations (the gettering may be abbreviated to “EG” hereinafter); and intrinsic gettering of forming oxygen-precipitated defects in a crystal substrate of a wafer, and capturing cations by the oxygen-precipitated defects to remove the cations (the gettering may be abbreviated to “IG” hereinafter).
However, as the wafers have become thinner in recent years, advantageous effects of IG have been become smaller. Additionally, by removing strain in the rear surface of a wafer, which causes a crack or warp of the wafer, advantageous effects of EG come not to be gained. For these reasons, there has been a problem that sufficient advantageous effects of the getterings come not to be gained.
Hitherto, as a method for bonding semiconductor elements onto a substrate or the like, the following have been suggested: a method using a thermosetting paste resin (see, for example, JP 2002-179769 A); or a method using an adhesive sheet wherein a thermoplastic resin and a thermosetting resin are used together with each other (see, for example, JP 2000-104040 A).
An adhesive sheet containing an anion exchanger and captures chloride ions that cause corrosion of a wire to improve connection reliability, and the like have been conventionally proposed in, for example, Japanese Patent Application Laid-Open (JP-A) No. 2009-256630 (especially in claim 1 and paragraph 0044), JP-A No. 2009-127042 (especially in claim 1 and paragraph 0054), and JP-A No. 2010-116453 (especially in claim 1 and paragraph 0027). A pressure-sensitive adhesive sheet, in which an ion scavenger for capturing chloride ions and the like is added to improve humidity and heat resistance when a voltage is applied, has been conventionally proposed as an adhesive sheet in JP-A No. 2009-203338 (especially claim 1 and paragraphs 0019 and 0050).